1. Field of the Invention
The present invention relates to an apparatus and method for sequentially forming a plurality of plastic bags from a continuous layflat tubular film of plastic material and for the accurate stacking of the plastic bags.
The utilization of plastic bags as an attractive alternative to the widely employed paper bags has formed widespread application, particularly in many retailing establishments and supermarkets. Basically, plastic bags are employed because of their attractiveness and their adaptability to having carrying handles integrally formed with the bag so as to render easier to lift and carry when filled with merchandise. Moreover, plastic bags generally evidence a higher strength in comparison with paper bags, and are impervious to moisture which will frequently cause paper bags to tear so as to result in spillage and possible damage to the bagged merchandise.
Inasmuch as plastic bags are usually formed from a plastic film material which is rather thin and of a limp easily crumpled nature, it is desirable that, prior to their individual use, such bags be stored and transported in accurately assembled stacks, consisting of large numbers of such plastic bags and which will facilitate the handling thereof by shipping and retailing personnel.
Consequently, there is a demand for apparatus and methods for rapidly and efficiently manufacturing such plastic bags from plastic film, and to superimpose and seal together the plastic bags into a coherent stack for easy handling.
2. Discussion of the Prior Art
Apparatuses are presently known for the stacking of plastic bags which have been formed on intermittently operating types of bag making machines. Basically, a known method and apparatus consists in forming stacks of bags immediately in front of the seal roll of a bag former after the continuous layflat plastic film has been sealed. At that location, the bags are impaled on hot pins which seal individual bags together and retain the stacked plastic bags in position relative to each other. The completed stack is then removed by the action of a device which grips the stack at the leading end thereof and pulls it out from the stacking location. Inasmuch as the prior art methods contemplate such stacking and sealing together of the formed plastic bags immediately after the formation of the hot bag seals, there is no provision for a seal cooling section and it is difficult to maintain the hot seals of superimposed plastic bags separate before they touch each other. This will frequently cause the hot seals to adhere to each other and renders subsequent separation of individual plastic bags difficult or even impossible without damaging the bag seals, often rendering the bags useless. Furthermore, the time-consuming stack forming sequence in apparatuses of that type necessitates that during the removal of each formed stack, the operating cycle of the synchronously operating bag-forming machine must be interrupted, during which interval no bags are formed, thereby reducing the production efficiency of such apparatus.
Another method and apparatus employed in the prior art for the stacking of plastic bags which are sequentially produced from a continuous layflat tubular film of plastic material consists of in forming the hot bag seals extending transversely of the direction of the longitudinal movement of the plastic film and concurrently separating the film into individual bags each having sealed leading and trailing edges. Thereafter the bags are superimposed upon each other through the intermediary of a rotating paddle wheel which engages the surface of each sequentially fed bag and superimposes it upon precedingly formed bag. As with other types of apparatus, also in this instance, when the formed stack of bags are to be removed, there is required a time-consuming interruption in the operating cycle of the bag-forming machine. Moreover, there is no firm interconnection provided between the individual bag of the bag stack which would preclude any slipping off or displacement of other bags in the stack prior to and during removal of the individual uppermost bag in the stack.